Hitherto, uniaxial eccentric screw pumps as disclosed in Patent Literatures 1 to 3 have been provided. In the uniaxial eccentric screw pump disclosed in Patent Literature 1 (JP 2012-154215 A), a rotor constructing a pump mechanism is connected to a power source through intermediation of a coupling rod. Thus, the rotor is revolvable (rotatable eccentrically) while being rotated about its axis.
Further, in the uniaxial eccentric screw pump disclosed in Patent Literature 2 (JP 5070515 B2), a rotor drive mechanism is provided between a power source side and a rotor, to thereby allow rotation of the rotor about its axis and revolution of the rotor. The rotor drive mechanism used in this uniaxial eccentric screw pump is a so-called planetary gearing mechanism or other such mechanism.
Further, in the uniaxial eccentric screw pump disclosed in Patent Literature 3 (JP 2009-047061 A), a rotation speed control driving portion for rotating a rotor about its axis and a revolution speed control driving portion for revolving the rotor are provided independently of each other. In this uniaxial eccentric screw pump, control of synchronizing operations of respective motors serving as the rotation speed control driving portion and the revolution speed control driving portion is executed, to thereby revolve the rotor while rotating the rotor about its axis.
In the above-mentioned related-art uniaxial eccentric screw pumps of Patent Literature 1 and Patent Literature 3, it is necessary to provide an elongated rod such as the coupling rod. For this reason, the related-art uniaxial eccentric screw pumps have a problem in that the total length is increased and the uniaxial eccentric screw pump is therefore upsized. Concomitantly with this problem, the related-art uniaxial eccentric screw pumps have another problem in that, when the pumping of fluid is stopped, the amount of fluid remaining in a pump casing is increased.
Further, when the independent drive sources are provided as the drive source for rotating the rotor about its axis and the drive source for revolving the rotor as in the above-mentioned uniaxial eccentric screw pump of Patent Literature 3, there is a problem in that the apparatus structure and the operation control become complicated accordingly. Similarly, also when the so-called planetary gearing mechanism or other such mechanism is arranged between the power source side and the rotor as the rotor drive mechanism as in the above-mentioned related-art uniaxial eccentric screw pump of Patent Literature 2, there is a problem in that the apparatus structure becomes complicated.
In view of the above, the present invention has an object to provide a uniaxial eccentric screw pump having a simple and compact apparatus structure and being capable of rotating a rotor about its axis and revolving the rotor without involving complicated operation control.